Search for Transient Astrophysical Neutrino Emission with IceCube-DeepCore

32 Pages·2015·0.83 MB·English

Search for Transient Astrophysical Neutrino Emission with
IceCube-DeepCore
IceCube Collaboration: M. G. Aartsen1, K. Abraham2, M. Ackermann3, J. Adams4,
J. A. Aguilar5, M. Ahlers6, M. Ahrens7, D. Altmann8, T. Anderson9, I. Ansseau5,
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M. Archinger10, C. Arguelles6, T. C. Arlen9, J. Auffenberg11, X. Bai12, S. W. Barwick13,
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V. Baum10, R. Bay14, J. J. Beatty15,16, J. Becker Tjus17, K.-H. Becker18, E. Beiser6,
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D S. BenZvi6, P. Berghaus3, D. Berley19, E. Bernardini3, A. Bernhard2, D. Z. Besson20,

4 G. Binder21,14, D. Bindig18, M. Bissok11, E. Blaufuss19, J. Blumenthal11, D. J. Boersma22,

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E C. Bohm7, M. Bo¨rner23, F. Bos17, D. Bose24, S. Bo¨ser10, O. Botner22, J. Braun6,
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L. Brayeur25, H.-P. Bretz3, N. Buzinsky26, J. Casey27, M. Casier25, E. Cheung19,
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p D. Chirkin6, A. Christov28, K. Clark29, L. Classen8, S. Coenders2, D. F. Cowen9,30,
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r A. H. Cruz Silva3, J. Daughhetee27, J. C. Davis15, M. Day6, J. P. A. M. de Andr´e31,
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a C. De Clercq25, E. del Pino Rosendo10, H. Dembinski32, S. De Ridder33, P. Desiati6,
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2 K. D. de Vries25, G. de Wasseige25, M. de With34, T. DeYoung31, J. C. D´ıaz-V´elez6,
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. A. Fedynitch17, J. Feintzeig6, J. Felde19, K. Filimonov14, C. Finley7, T. Fischer-Wasels18,
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5 S. Flis7, C.-C. Fo¨sig10, T. Fuchs23, T. K. Gaisser32, R. Gaior36, J. Gallagher37,
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A. Groß2, C. Ha21,14, C. Haack11, A. Haj Ismail33, A. Hallgren22, F. Halzen6, E. Hansen38,
B. Hansmann11, K. Hanson6, D. Hebecker34, D. Heereman5, K. Helbing18, R. Hellauer19,
S. Hickford18, J. Hignight31, G. C. Hill1, K. D. Hoffman19, R. Hoffmann18, K. Holzapfel2,
A. Homeier39, K. Hoshina6,49, F. Huang9, M. Huber2, W. Huelsnitz19, P. O. Hulth7,
K. Hultqvist7, S. In24, A. Ishihara36, E. Jacobi3, G. S. Japaridze40, K. Jero6, M. Jurkovic2,
A. Kappes8, T. Karg3, A. Karle6, M. Kauer6,41, A. Keivani9, J. L. Kelley6, J. Kemp11,
– 2 –
A. Kheirandish6, J. Kiryluk42, J. Kla¨s18, S. R. Klein21,14, G. Kohnen43, R. Koirala32,
H. Kolanoski34, R. Konietz11, L. Ko¨pke10, C. Kopper26, S. Kopper18, D. J. Koskinen38,
M. Kowalski34,3, K. Krings2, G. Kroll10, M. Kroll17, J. Kunnen25, N. Kurahashi44,
T. Kuwabara36, M. Labare33, J. L. Lanfranchi9, M. J. Larson38, M. Lesiak-Bzdak42,
M. Leuermann11, J. Leuner11, L. Lu36, J. Lu¨nemann25, J. Madsen45, G. Maggi25,
K. B. M. Mahn31, R. Maruyama41, K. Mase36, H. S. Matis21, R. Maunu19, F. McNally6,
K. Meagher5, M. Medici38, A. Meli33, T. Menne23, G. Merino6, T. Meures5, S. Miarecki21,14,
E. Middell3, E. Middlemas6, L. Mohrmann3, T. Montaruli28, R. Morse6, R. Nahnhauer3,
U. Naumann18, G. Neer31, H. Niederhausen42, S. C. Nowicki26, D. R. Nygren21,
A. Obertacke18, A. Olivas19, A. Omairat18, A. O’Murchadha5, T. Palczewski46,
H. Pandya32, D. V. Pankova9, L. Paul11, J. A. Pepper46, C. P´erez de los Heros22,
C. Pfendner15, D. Pieloth23, E. Pinat5, J. Posselt18, P. B. Price14, G. T. Przybylski21,
J. Pu¨tz11, M. Quinnan9, C. Raab5, L. Ra¨del11, M. Rameez28, K. Rawlins47, R. Reimann11,
M. Relich36, E. Resconi2, W. Rhode23, M. Richman44, S. Richter6, B. Riedel26,
S. Robertson1, M. Rongen11, C. Rott24, T. Ruhe23, D. Ryckbosch33, S. M. Saba17,
L. Sabbatini6, H.-G. Sander10, A. Sandrock23, J. Sandroos10, S. Sarkar38,48, K. Schatto10,
F. Scheriau23, M. Schimp11, T. Schmidt19, M. Schmitz23, S. Schoenen11, S. Sch¨oneberg17,
A. Sch¨onwald3, L. Schulte39, D. Seckel32, S. Seunarine45, M. W. E. Smith9, D. Soldin18,
M. Song19, G. M. Spiczak45, C. Spiering3, M. Stahlberg11, M. Stamatikos15,50, T. Stanev32,
N. A. Stanisha9, A. Stasik3, T. Stezelberger21, R. G. Stokstad21, A. Sto¨ßl3, R. Stro¨m22,
N. L. Strotjohann3, G. W. Sullivan19, M. Sutherland15, H. Taavola22, I. Taboada27,
J. Tatar21,14, S. Ter-Antonyan35, A. Terliuk3, G. Teˇsi´c9, S. Tilav32, P. A. Toale46,
M. N. Tobin6, S. Toscano25, D. Tosi6, M. Tselengidou8, A. Turcati2, E. Unger22, M. Usner3,
S. Vallecorsa28, J. Vandenbroucke6, N. van Eijndhoven25, S. Vanheule33, J. van Santen3,
J. Veenkamp2, M. Vehring11, M. Voge39, M. Vraeghe33, C. Walck7, A. Wallace1,
M. Wallraff11, N. Wandkowsky6, Ch. Weaver26, C. Wendt6, S. Westerhoff6, B. J. Whelan1,
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N. Whitehorn6, K. Wiebe10, C. H. Wiebusch11, L. Wille6, D. R. Williams46, H. Wissing19,
M. Wolf7, T. R. Wood26, K. Woschnagg14, D. L. Xu46, X. W. Xu35, Y. Xu42, J. P. Yanez3,
G. Yodh13, S. Yoshida36, and M. Zoll7
– 4 –
1Department of Physics, University of Adelaide, Adelaide, 5005, Australia
2Technische Universita¨t Mu¨nchen, D-85748 Garching, Germany
3DESY, D-15735 Zeuthen, Germany
4Dept. of Physics and Astronomy, University of Canterbury, Private Bag 4800,
Christchurch, New Zealand
5Universit´e Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels, Belgium
6Dept. of Physics and Wisconsin IceCube Particle Astrophysics Center, University of
Wisconsin, Madison, WI 53706, USA
7Oskar Klein Centre and Dept. of Physics, Stockholm University, SE-10691 Stockholm,
Sweden
8Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universita¨t Erlangen-
Nu¨rnberg, D-91058 Erlangen, Germany
9Dept. of Physics, Pennsylvania State University, University Park, PA 16802, USA
10Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz, Germany
11III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany
12Physics Department, South Dakota School of Mines and Technology, Rapid City, SD
57701, USA
13Dept. of Physics and Astronomy, University of California, Irvine, CA 92697, USA
14Dept. of Physics, University of California, Berkeley, CA 94720, USA
15Dept. of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State Uni-
versity, Columbus, OH 43210, USA
16Dept. of Astronomy, Ohio State University, Columbus, OH 43210, USA
17Fakult¨at fu¨r Physik & Astronomie, Ruhr-Universita¨t Bochum, D-44780 Bochum, Ger-
many
18Dept. of Physics, University of Wuppertal, D-42119 Wuppertal, Germany
19Dept. of Physics, University of Maryland, College Park, MD 20742, USA
– 5 –
20Dept. of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA
21Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
22Dept. of Physics and Astronomy, Uppsala University, Box 516, S-75120 Uppsala, Sweden
23Dept. of Physics, TU Dortmund University, D-44221 Dortmund, Germany
24Dept. of Physics, Sungkyunkwan University, Suwon 440-746, Korea
25Vrije Universiteit Brussel, Dienst ELEM, B-1050 Brussels, Belgium
26Dept. of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2E1
27School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Tech-
nology, Atlanta, GA 30332, USA
28D´epartement de physique nucl´eaire et corpusculaire, Universit´e de Gen`eve, CH-1211
Gen`eve, Switzerland
29Dept. of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7
30Dept. of Astronomy and Astrophysics, Pennsylvania State University, University Park,
PA 16802, USA
31Dept. of Physics and Astronomy, Michigan State University, East Lansing, MI 48824,
USA
32Bartol Research Institute and Dept. of Physics and Astronomy, University of Delaware,
Newark, DE 19716, USA
33Dept. of Physics and Astronomy, University of Gent, B-9000 Gent, Belgium
34Institut fu¨r Physik, Humboldt-Universita¨t zu Berlin, D-12489 Berlin, Germany
35Dept. of Physics, Southern University, Baton Rouge, LA 70813, USA
36Dept. of Physics, Chiba University, Chiba 263-8522, Japan
37Dept. of Astronomy, University of Wisconsin, Madison, WI 53706, USA
38Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
39Physikalisches Institut, Universit¨at Bonn, Nussallee 12, D-53115 Bonn, Germany
40CTSPS, Clark-Atlanta University, Atlanta, GA 30314, USA
– 6 –
Received ; accepted
41Dept. of Physics, Yale University, New Haven, CT 06520, USA
42Dept. of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800,
USA
43Universit´e de Mons, 7000 Mons, Belgium
44Dept. of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
45Dept. of Physics, University of Wisconsin, River Falls, WI 54022, USA
46Dept. of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA
47Dept. of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Dr.,
Anchorage, AK 99508, USA
48Dept. of Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK
49Earthquake Research Institute, University of Tokyo, Bunkyo, Tokyo 113-0032, Japan
50NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
– 7 –
ABSTRACT
We present the results of a search for astrophysical sources of brief transient
neutrino emission using IceCube and DeepCore data acquired between May 15th
2012 and April 30th 2013. While the search methods employed in this analysis
are similar to those used in previous IceCube point source searches, the data
set being examined consists of a sample of predominantly sub-TeV muon neu-
trinos from the Northern Sky (-5◦ < δ < 90◦) obtained through a novel event
selection method. This search represents a first attempt by IceCube to identify
astrophysical neutrino sources in this relatively unexplored energy range. The
reconstructed direction and time of arrival of neutrino events is used to search for
any significant self-correlation in the dataset. The data revealed no significant
source of transient neutrino emission. This result has been used to construct
limits at timescales ranging from roughly 1s to 10 days for generic soft-spectra
transients. We also present limits on a specific model of neutrino emission from
soft jets in core-collapse supernovae.
Subject headings: neutrino astronomy, neutrinos, GRB, supernova, astroparticle
physics
– 8 –
1. Introduction
The nascent field of high-energy neutrino astronomy opens the possibility of answering
several open questions in astrophysics due in large part to the neutrino’s ability to escape
the densest regions of astrophysical environments. Specifically, the detection of transient
astrophysical neutrino sources will help shed light on the acceleration mechanisms at work
in some of the most energetic phenomena in the Universe such as gamma-ray bursts,
supernovae, and active galactic nuclei. Previous attempts to detect such sources with the
IceCube Neutrino Observatory (Achterberg et al. 2006) are most sensitive to neutrino
fluxes above 1 TeV with poor sensitivity below 100 GeV. Searches for astrophysical
sources at lower energies (1–100 GeV) have been performed by Super-Kamiokande (Thrane
et al. 2009), however the detector’s 50 kton instrumented volume limits its sensitivity
to astrophysical neutrino fluxes. A newly developed 30–300 GeV muon neutrino sample
collected by IceCube and its low energy extension DeepCore (Abbasi et al. 2012b) enhances
IceCube’s sensitivity in this under-explored energy range. In this paper we will present the
results of a search for transient neutrino emission in this GeV-scale neutrino sample.
The detection of astrophysical neutrino sources is a primary design goal of the IceCube
Neutrino Observatory (Achterberg et al. 2006). Located at the geographic South Pole,
IceCube utilizes the clear Antarctic glacial ice ice cap as a detection medium for the
Cherenkov light produced by secondary products of neutrino interactions. The detector
consists of 5,160 Digital Optical Modules (DOMs) distributed among 86 cables or “strings”
to form a 1 km3 instrumented volume. These DOMs house photomultiplier tubes (PMTs),
to detect Cherenkov photons, as well as digitizing electronics for initial processing of the
PMT data (Abbasi et al. 2009). A centrally located region of denser instrumentation
featuring DOMs with more sensitive PMTs comprises the DeepCore sub-array. This
extension to the IceCube array enhances the detector’s response to lower energy neutrino
– 9 –
events.
Typical searches for astrophysical sources with IceCube make use of a sample primarily
comprised of an irreducible background of high-energy atmospheric muon neutrinos (E (cid:38) 1
ν
TeV) to look for both steady (Aartsen et al. 2014b) and transient sources (Aartsen et al.
2015). As of yet, these searches have not found any significant self-correlations within the
data sample nor correlations between the neutrino data and known astrophysical objects of
interest. So far, these analyses have largely eschewed low energy neutrino events collected
by DeepCore for two reasons. First, the poorer angular resolution of these events renders
them less suitable for pointing analyses. Second, the soft spectrum of the atmospheric
neutrino flux results in higher rate of background neutrino events. However, the increased
background can be somewhat mitigated by searching solely for transient sources. Therefore,
applying previously developed search techniques (Braun et al. 2010) to a sample of low
energy (30 GeV E < 300 GeV) muon neutrino events from DeepCore can enhance
ν
≤
IceCube’s sensitivity to short transient neutrino sources with softer spectra.
Due to the large atmospheric neutrino background in this energy range, searches using
a data set composed of these low energy events will only be sensitive to emission timescales
on the order of one day or shorter. Active galactic nuclei (AGN) undergoing flaring events
are one potential source for emission on this timescale. Protons may be accelerated in
relativistic jets, powered by accretion onto the AGN, resulting in the production of pions
(and subsequently neutrinos) in shocks due to proton-photon interactions and proton
self-collisions (Becker & Biermann 2009). For some of the timescales under consideration in
this search, AGN-powered hadron acceleration must occur over a compact region and will
require very large acceleration gradients (Klein et al. 2013). The presence of these large
gradients will result in significant acceleration of muons prior to decay, leading to spectral
hardening of the neutrino flux. Thus, if neutrino emission is occurring over short timescales,
– 10 –
it will feature enhanced visibility at higher energies.
Sub-photospheric neutrino emission from gamma-ray bursts (GRBs) represents another
possible source for this search. A model for photospheric gamma-ray emission in GRBs
by Murase et al. (2013) suggests that a substantial flux of 100 GeV-scale neutrinos may
be produced during the initial stages of relativistic outflow in the GRB. Decoupling of
protons and neutrons during the initial formation of the relativistic jet causes hadronuclear
collisions resulting in the production of pions and the production of neutrinos via pion
decay. The predicted energy for the neutrinos produced in these sub-photospheric collisions
is on the order of 100 GeV, and therefore this GRB neutrino flux may only be visible to
IceCube searches with the inclusion of sub-TeV neutrino events.
Perhaps the most promising potential source for this study is a special class of
core-collapse supernova referred to as choked GRBs (M´esz´aros & Waxman 2001). The
standard GRB model assumes that relativistic jets are generated during the accretion of
material onto the compact object formed during core-collapse (Rees & Meszaros 1992).
Fermi-acceleration of charged particles occurs within the internal shocks of these jets leading
to gamma ray emission once the jets breach the surrounding stellar envelope. There is an
observed correlation between long duration GRBs and core-collapse supernovae (CC SNe)
((Woosley & Bloom 2006), (Modjaz 2011)). While the observed fraction of SNe resulting in
the occurrence of a GRB is quite low, it may be that a larger fraction of core-collapse SNe
still manage to produce mildly relativistic jets. Due to insufficient energy, these jets fail to
break through the stellar envelope and any gamma ray emission is effectively ‘choked’ off.
If protons are accelerated in these jets, then neutrino production will occur in the shocks of
the jet irrespective of whether or not the jet successfully escapes. A model of this neutrino
emission proposed by Razzaque et al. (2004) and extended upon by Ando & Beacom
(2005), hereafter referred to as the RMW/AB model, suggests that these neutrinos may be